HPLC for Food Analysis phần 2 ppsx

3 Sample preparation filtration Column 300 x 7.8 mm BioRad HPX 87-H, 9 µm Mobile phase 0.0035 M H 2 SO 4 isocratic Flow rate 0.6 ml/min Column compartment 65 °C Injection volume 10 µl Detector UV-VWD detection wavelength 192 nm or 210 nm Conditions as above except Mobile phase 0.007 M H 2 SO 4 isocratic Detector UV-DAD 4. Official Methods of Analysis, Food Compositions; Additives, Natural Contaminants, 15th ed; AOAC: Arlington, VA, 1990, Vol. 2.; Official Method AOAC 986.13: quinic, malic, citric acid in cranberry juice cocktail and apple juice. Figure 2 Analysis of acidulants in white wine Figure 3 Analysis of citric acid in vodka 100 mAU 0 0 51015 20 0 190 match 994 Wavelength [nm] 276 20 Citric acid Sample spectrum overlaid with library spectrum Citric acid Glucose Fructose Ethanol Time [min] 0 5 10 15 20 25 mAU 0 100 200 300 400 White wine Standard Oxalic acid Citric acid Tartaric acid Malic acid Sulfur-trioxide Succinic acid ? ? ? ? ? 1 2 3 4 5 6 Lactic acid Glycerol DEG Acetic acid Methanol Ethanol 7 8 9 10 11 12 1 2 3 4 5 7 8 9 6 10 11 12 Time [min]  HPLC method performance Limit of detection 100 ng injected amount, S/N = 2 equivalent to 2 ppm with 50 µl injected volume Repeatability of RT over 10 runs < 0.1 % areas over 10 runs < 3 % Antioxidants The following compounds are used as antioxidants in food products: 4 Natural antioxidants: • vitamin C • vitamin E Synthetic antioxidants: • BHT butylated hydroxytoluene • BHA butylated hydroxyanisole • TBHQ mono-tert-butylhydroquinone • THBP 2,4,5-trihydroxybutyrophenone • PG propyl gallate • OG octyl gallate • DG dodecyl gallate • Ionox-100 4-hydroxymethyl-2,6-di(tert-butyl)phenol • NDGA nordihydroguaiaretic acid • TDPA 3,3'-thiodipropionic acid • ACP ascorbyl-palmitate Antioxidants may be naturally present in food, or they may be formed by processes such as smoking. Examples of natural antioxidants include tocopherols (vitamin E) and acsorbic acid (vitamin C). A second category of antioxidants comprises the wholly synthetic antioxidants. When these antioxidants are added to foodstuffs, they retard the onset of rancidity by preventing the oxidative degradation of lipids. In most countries where antioxidants are permitted either singly or as combinations in foodstuffs, maximum levels for these compounds have been set. Sample preparation Sample preparation depends strongly on the matrix to be analyzed. For samples low in fat, liquid extraction with ultrasonic bath stimulation can be used. For samples with more complex matrices, solid-phase extraction, liquid/liquid extraction, or steam distillation may be necessary. 4 1 Chromatographic conditions HPLC and UV-visible diode-array detection have been applied in the analysis of antioxidants in chewing gum. Spectral information and retention times were used for identification. 5 Sample preparation ultrasonic liquid extraction with acetonitrile (ACN) Column 1 100 x 4 mm BDS, 3 µm Mobile phase A = water + 0.2 ml H 2 SO 4 , pH = 2.54 B = ACN Gradient start with 10 % B at 3 min 60 % B at 4 min 80 % B at 11 min 90 % B Flow rate 0.5 ml/min Post time 4 min Column compartment 30 °C Injection volume 5 µl Detector UV-DAD detection wavelength 260/40 nm, reference wavelength 600/100 nm 4. Official Methods of Analysis, Food Compositions; Additives, Natural Contaminants, 15th ed; AOAC: Arlington, VA, 1990, Vol. 2.; AOAC Official Method 983.15: Antioxidants in oils and fats. 5 mAU 1500 1000 500 0 2 4 6 8 10 12 2 1 3 4 6 8 7 1 Vitamin C 2 PG 3 THBP 4 TBHQ 5 BHA 6 4-hydroxy 7 BHT 8 ACP Chewing gum extract Standard Time [min] Quaternary pump + vacuum degasser Control and data evaluation Water Acetonitrile Column compart- ment Auto- sampler Diode- array detector HPLC method performance Limit of detection 0.1–2 ng (injected amount), S/N = 2 Repeatability of RT over 10 runs < 0.2 % areas over 10 runs < 1 % Figure 4 Analysis of antioxidants in chewing gum  Preservatives The following compounds are used as preservatives in food products: • benzoic acid • sorbic acid • propionic acid • methyl-, ethyl-, and propylesters of p-hydroxy benzoic acid (PHB-methyl, PHB-ethyl, and PHB-propyl, respectively) 4 Preservatives inhibit microbial growth in foods and beverages. Various compound classes of preservatives are used, depending on the food product and the expected microorganism. PHBs are the most common preservatives in food products. In fruit juices, in addition to sulfur dioxide, sorbic and benzoic acid are used as preservatives, either individually or as a mixture. Sample preparation Sample preparation depends strongly on the matrix to be analyzed. For samples low in fat, liquid extraction with ultrasonic bath stimulation can be used. For samples with more complex matrices, solid-phase extraction, liquid/liquid extraction, or steam distillation may be necessary. 6 1 Quaternary pump + vacuum degasser Control and data evaluation Water Acetonitrile Column compart- ment Auto- sampler Diode- array detector Chromatographic conditions HPLC and UV-visible diode-array detection have been applied in the analysis of preservatives in white wine and salad dressing. Spectral information and retention times were used for identification. 7 Sample preparation Carrez clearing and filtration for the salad dressing. None for white wine. Column 125 x 4 mm Hypersil BDS, 5 µm Mobile phase A = water + 0.2 ml H 2 SO 4 , pH = 2.3 B = ACN Gradient start with 10 % B at 3 min 60 % B at 4 min 80 % B at 6 min 90 % B at 7 min 10 % B Flow rate 2 ml/min Post time 1 min Column compartment 40 °C Injection volume 2 µl Detector UV-DAD detection wavelength 260/40 nm 4. Official Methods of Analysis, Food Compositions; Additives, Natural Contaminants, 15th ed; AOAC: Arlington, VA, 1990, Vol. 2.; AOAC Official Method 979.08: Benzoate, caffeine, saccharine in carbonated beverages.  PHB-propyl Absorbance (scaled) library Spectral library match 999 50 30 10 200 320 Wavelength [nm] sample Standard White wine Salad dressing mAU 60 50 40 30 20 10 0 1 2 34 Time [min] Sorbic acid PHB-methyl PHB-ethyl BHA BHT Benzoic acid Figure 5 Analysis of preservatives in white wine and salad dressing HPLC method performance Limit of detection 10 ppm, S/N = 2 Repeatability of RT over 10 runs < 0.1 % areas over 10 runs < 3 % Artificial sweeteners The following compounds are used as artificial sweeteners in food products: • acesulfam • aspartame • saccharin 4 Nowadays, low-calorie sweeteners are widely used in foods and soft drinks. Investigations of the toxicity of these compounds have raised questions as to whether they are safe to consume. As a result, their concentration in foods and beverages is regulated through legislation in order to prevent excessive intake. Sample preparation Sample preparation depends strongly on the matrix to be analyzed. For sample low in fat, liquid extraction at low pH with ultrasonic bath stimulation can be used. For samples with more complex matrices, solid-phase extraction, liquid/liquid extraction, or steam distillation may be necessary. 8 1 Quaternary pump + vacuum degasser Control and data evaluation Water Methanol Column compart- ment Auto- sampler Diode- array dete Fluores- cence detector ctor Chromatographic conditions The HPLC method presented here for the analysis of aspartame is based on automated on-column derivatization and reversed-phase chromatography. UV spectra were evaluated as an additional identification tool. 5 9 Derivatization agent o-phthalaldehyde (OPA) mercapto-propionic acid (MPA) Column 100 x 2.1 mm Hypersil ODS, 5 µm Mobile phase A = 0.01 mM sodium acetate B = methanol Gradient start with 5 % B at 5 min 25 % B at 10 min 35 % B at 13 min 55 % B at 18 min 80 % B at 20 min 95 % B Flow rate 0.35 ml/min Post time 5 min Column compartment 40 °C Injection volume 1 µl Injector program for online derivatization 1. Draw 5.0 µl from vial 3 (borate buffer) 2. Draw 0.0 µl from vial 0 (water) 3. Draw 1.0 µl from vial 1 (OPA/MPA) 4. Draw 0.0 µl from vial 0 (water) 5. Draw 1.0 µl from sample 6. Mix 7 µl (6 cycles) 7. Inject Detectors UV-DAD: detection wavelength 338/20 nm or fluorescence: excitation wavelength 230 nm, emission wavelength 445 nm 5. A.M. Di Pietra et al., “HPLC analysis of aspartame and saccharin in pharmaceutical and dietary formulations”; Chromatographia, 1990, 30, 215–219. 4. Official Methods of Analysis, Food Compositions; Additives, Natural Contaminants, 15th ed; AOAC: Arlington, VA, 1990, Vol. 2.; Official Method AOAC 979.08: Benzoate, caffeine, saccharin in soda beverages.  0 10 20 30 40 50 Time [min] 0246810 Aspartame spectra original derivatized scaled 250 300 350 400 Wavelength [nm] mAU 60 Aspartame Figure 6 Chromatogram and spectra of derivatized and non derivatized aspartame HPLC method performance Limit of detection for fluorescence 200 pg (injected amount), S/N = 2 for DAD 1 ng (injected amount), S/N = 2 Repeatability of RT over 10 runs < 0.1 % of areas over 10 runs < 5 % Colorants We have selected the food color E104 Quinolin yellow and E131 Patent blue as application examples. Synthetic colors are widely used in the food processing, pharmaceutical, and chemical industries for the following purposes: 4 • to mask decay • to redye food • to mask the effects of aging The regulation of colors and the need for quality control requirements for traces of starting product and by-products have forced the development of analytical methods. Nowa- days, HPLC methods used are based on either ion-pairing reversed-phase or ion-exchange chromatography. UV absorption is the preferred detection method. The UV absorption maxima of colors are highly characteristic. Maxima start at approximately 400 nm for yellow colors, 500 nm for red colors, and 600–700 nm for green, blue, and black colors. For the analysis of all colors at maximum sensitivity and selectivity, the light output from the detector lamp should be high for the entire wavelength range. However, this analysis is not possible with conventional UV-visible detectors based on a one-lamp design. Therefore, we have chosen a dual-lamp design based on one deuterium and one tungsten lamp. This design ensures high light output for the entire wavelength range. Sample preparation Whereas turbid samples require filtration, solid samples must be treated with 0.1 % ammonia in a 50 % ethanol and water mixture, followed by centrifugation. Extraction is then performed using the so-called wool-fiber method. After desorption of the colors and filtration, the solution can be injected directly into the HPLC instrument. 10 1 Water Acetonitrile Column compart- ment Auto- sampler Quaternary pump + vacuum degasser Control and data evaluation Diode- array detector Chromatographic conditions The HPLC method presented here for the analysis of dyes is based on ion-pairing reversed-phase chromatography. UV spectra were evaluated as an additional identification tool. 6 11 Sample preparation injection without further preparation Column 125 x 3 µm Hypersil BDS, 3 mm Mobile phase A = 0.01 M NaH 2 PO 4 + 0.001 M tetrabutyl- ammoniumdihydrogen- phosphate, pH = 4.2 B = ACN Gradient start with 15 % in 10 min to 40 % in 14 min to 90 % until 19 min at 90 % in 20 min to 15 % ACN Stop time 20 min Post time 4 min Flow rate 0.8 ml/min Column compartment 40 °C Injection volume 1 µl Detector UV-DAD signal A: 254/50 nm (for optimization of separation) signal B: 350/20 nm signal C: 465/30 nm signal D: 600/40 nm 4. Official Methods of Analysis, Food Compositions; Additives, Natural Contaminants, 15th ed; AOAC: Arlington, VA, 1990, Vol. 2.; Official Method AOAC 981.13: Cresidine sulfonic acid in FD&C Red No. 40; Official Method AOAC 982.28: Intermediates and reaction by-products in FD&Y Yellow No. 5; Official Method AOAC 977.23: 44’ (Diazoamino) dibenzene sulfonic acid (DAADBSA) in FD&C Yellow No. 6; Official Method AOAC 980.24: Sulfanilic acid in FD&C Yellow No. 6. 6. A.G. Huesgen, R.Schuster, “Sensitive analysis of synthetic colors using HPLC and diode-array detection at 190–950 nm”, Agilent Application Note 5964-3559E, 1995.  0 24 6 810 12 14 mAU 2 4 6 8 10 12 465 nm/30 nm 600 nm/40 nm Patent blue Chinolin yellow Time [min] Woodruff lemonade Spectra of different colors 300 400 500 600 700 800 Norm 0 10 20 30 40 Patent blue Brilliant Amaranth red Tartrazine yellow Wavelength [nm] blue Figure 7 Analysis of synthetic colors in lemonade. Overlay of spectra of yellow, red, blue and “black” colors HPLC method performance Limit of detection 2 ng (injected amount) for UV-DAD S/N = 2 Repeatability of RT over 10 runs < 0.2 % of areas over 10 runs < 3 % Flavors The following compounds are examples of flavoring agents used in food products: • lupulon and humulon (hop bittering compounds) • vanillin • naringenin and hesperidin (bittering compounds) Three major classes of compounds are used as flavoring agents: essential oils, bitter compounds, and pungency compounds. Although the resolution afforded by gas chromatography (GC) for the separation of flavor compounds remains unsurpassed, HPLC is the method of choice if the compound to be analyzed is low volatile or thermally unstable. Sample preparation Turbid samples require filtration, whereas solid samples must be extracted with ethanol. After filtration, the solution can be injected directly into the HPLC instrument. 12 1 Vanillin Quaternary pump + vacuum degasser Control and data evaluation Water Acetonitrile Column compart- ment Auto- sampler Diode- array detector [...]... Orange juice 0 -5 0.5 1 1.5 2 Time [min] Figure 10 Analysis of bitter compounds in orange juice HPLC method performance Limit of detection for DAD Repeatability of RT over 10 runs of areas over 10 runs Standard 1 ng (injected amount), S/N = 2 < 0 .2 % < 1 % 8 Official Methods of Analysis; Horwitz, W., Ed.; 14th ed.; AOAC: Arlington, VA, 1984; secs 12. 018– 12. 021 14 2. 5 Chapter 2 Analytical examples of residues... prepared according to Carrez 1 and 2 Column 125 x 4 mm Hypersil BDS, 5 µm Mobile phase A = water + 0.15 ml/l H2SO4 (conc.), pH = 2. 4 B = ACN Gradient start with 20 % B at 3 min 20 % B at 5 min 90 % B at 6 min 20 % B Flow rate 2 ml/min Post time 1 min Column compartment 40 °C Injection volume 1 µl Detector UV-DAD detection wavelength 26 0/80 nm, reference wavelength 380/80 nm mAU 20 Naringenin 15 Hesperidin... vanilla-containing products using HPLC ; J Chromatogr., 19 82, 24 6, 313–316 13 1 Bitter compounds: hesperidin and naringenin Sample preparation for bitter compounds in orange juice8 The samples were prepared according to Carrez 1 and 2 This method uses potassium ferrocyanide and zinc sulfate for protein precipitation Chromatographic conditions The HPLC method presented here for the analysis of hesperidin and... 50 40 30 20 30 50 Vanillin Limit of detection 0 .2 5 ng (injected amount) S/N = 2 Repeatability of RT over 10 runs < 0 .2 % of areas over 10 runs < 1 % Match 991 21 7 Wavelength [nm] 400 Salicylaldehyde 20 HPLC method performance Vanillin 10 0 Syringaaldehyde Gallic acid 10 Standard Cognac 0 0 2 4 Time [min] 6 8 10 Figure 9 Analysis of vanillin in cognac Identification of vanillin through spectra comparison... phase A = water + 0.15 ml H2SO4 (conc.), pH = 2. 3 B = ACN Gradient start with 10 % B at 3 min 40 % B at 4 min 40 % B at 6 min 80 % B at 7 min 90 % B Flow rate 0.8 ml/min Post time 3 min Column compartment 30 °C Injection volume 5 µl Detector UV-DAD detection wavelength 28 0/80 nm, reference wavelength 360/100 nm Chromatographic conditions The HPLC method presented here for the analysis of vanillin is based... 4-hydroxybenzaldehyde 300 20 0 Ethylvanillin Vanillin alcohol Coumarin Standard 100 Vanillin extract 0 0 1 2 3 4 Time [min] 5 6 7 Figure 8 Determination of the quality of vanillin extract Conditions as above, except Column 100 x 2. 1 mm Hypersil ODS, 5 µm Mobile phase A = water + 5 mM NaH2PO4 B = methanol Gradient at 10 min 70 % B Flow rate 0.4 ml/min mAU 60 40 50 40 30 20 30 50 Vanillin Limit of detection 0 .2 5 ng (injected... in many countries, including the United States, Germany, and Japan, have set tolerance levels for residues of these drugs Simple and reliable analysis methods are necessary in order to detect and quantify residues of chemotherapeutic and antiparasitic drugs in food products Malisch et al have developed an HPLC method to determine 11 of these compounds.9,10 The internal standard (ISTD) comprises benzothiazuron... protozoa, and/or fungi A number of chemotherapeutics are available for the prevention and control of these diseases After application, residues of these drugs can be found in foods of animal origin such as milk, eggs, and meat These chemotherapeutics can cause resistancy of bacteria Because of the toxic nature of chemotherapeutics, for example, choramphenical, government agencies in many countries,... amount), S/N = 2 < 0 .2 % < 1 % 8 Official Methods of Analysis; Horwitz, W., Ed.; 14th ed.; AOAC: Arlington, VA, 1984; secs 12. 018– 12. 021 14 2. 5 Chapter 2 Analytical examples of residues and contaminants 2 Residues of chemotherapeutics and antiparasitic drugs In addition to several other drugs, nitrofurans and sulfonamides such as sulfapyridine, N-acetyl metabolite, ethopabat, chloramphenicol, meticlorpindol, . acid Methanol Ethanol 7 8 9 10 11 12 1 2 3 4 5 7 8 9 6 10 11 12 Time [min]  HPLC method performance Limit of detection 100 ng injected amount, S/N = 2 equivalent to 2 ppm with 50 µl injected volume Repeatability. and non derivatized aspartame HPLC method performance Limit of detection for fluorescence 20 0 pg (injected amount), S/N = 2 for DAD 1 ng (injected amount), S/N = 2 Repeatability of RT over 10. 12. 018– 12. 021 .  Sample preparation The orange juice was prepared according to Carrez 1 and 2. Column 125 x 4 mm Hypersil BDS, 5 µm Mobile phase A = water + 0.15 ml/l H 2 SO 4 (conc.), pH = 2. 4 B